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CDMA vs WCDMA

Discussion in 'GENERAL Wireless Discussion' started by eternaltraveller, Sep 3, 2002.

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  1. eternaltraveller

    eternaltraveller New Member

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    Hi,

    I am currently doing some research into the differences between CDMA and WCDMA.

    Any Assistance would be greatly appreciated..

    Cheers,
    [​IMG]
     
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  2. Jimmy821

    Jimmy821 Member

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    Let's see...How much time ya got? IN a nutshell

    Basically, CDMA is what the US, parts of Asia, and some other places have for phone service. W-CDMA is what will be coming around, promising higher data rates, clearer calls, etc., by utlizing larger amounts of bandwidth and bigger bands in terms of frequency.

    In terms of the migration of the various systems (GSM, TDMA, CDMA) and what they will come to, due to demand, cost, etc., W-CDMA looks somewhat promising.

    Need more detail? http://www.cdg.org or http://www.ece.concordia.ca/Research/wcdma/project.html

    James
     
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  3. IdiOTeQnoLogY

    IdiOTeQnoLogY Bronze Senior Member
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    actually WCDMA is not looking too promising.........so far it has been filled with problems. perhaps what the user was asking was the difference between cdma2000 and wcdma?

    basically W-CDMA is a derivative of cdma but called WIDEBAND. basically qualcomm, a USA company has the sole patent rights to CDMA (which is a 2nd generation technology) as well as being the sole patent holder to cdma2000 (the next generation technology from cdma)

    the european carriers wanted a next generation technology, but didnt want to rely on one that only a usa company would make all the money off of the royalties.........so basically they concocted up W-CDMA.........and after some legal battles with qualcomm over patent stealing etc..........the europeans got their W-cdma with qualcomm making some of the royalties off of wcdma sales.

    so far japan i think is the only country to launch a commercial wcdma network on a large scale; and things are going not so well for them.whereas carriers who have gone with cdma2000 in korea and japan are raking in customers on those networks.........as well as in the USA Sprint and Verizon have launched large cdma2000 networks........there are some bugs but nothing like wcdma is facing so far. also Wcdma requires all new spectrum to use..........the Wideband in wcdma implies that it uses a wider band of spectrum and that is right. wcdma is not very efficient with spectrum;it requires 5mhz of specturm per channel to work from what i understand whereas cdma2000 can work on 1.25 or so mhz per chanel..........and spectrum in the usa is a pricey commodity.
     
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  4. Carajo

    Carajo New Member

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    As for your comment of WCDMA not looking to promising I would have to disagree with you. WCDMA or UMTS or what ever you might want to call it is looking better and better every day.

    In Japan there are 2 networks with UMTS (DoCoMo and J-Phone) and KDDI with CDMA 2000.... and I wouldn't say that CDMA 2000 has been a easy road to get where it is today... and its not the reason for KDDI raking in the customers either. [​IMG]

    As for the whole GSM vs CDMA battle...... in a voice only network, they are basically the same in terms of quality to the subscriber and cost to the service provider... when we move to a data network with high bit rates CDMA is the choice to go... and by using a broader band width in CDMA it allows for very high bit rates in a cost efective solution. (FYI I am not a Swede or work for Ericsson)

    Really WCDMA is CDMA........ Both uses the same prinples of CDMA........... so your comment of WCDMA not being efficeitn with specturm is not correct...... its CDMA they handle it the same way...... Basically (really basic) the reason for the wide band of 5MHz is the high data rates. 5MHz has much much much more capacity than 1.25 Mhz.... with simple calaclutions you can see this..........
     
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  5. Rasputin

    Rasputin Bronze Senior Member
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    Unless you can expand for me J-phone does not have an operational UMTS system running currently, I thought they were in the middle of GSM upgrade with GPRS. I do not consider the up to 384downlink and the up to 64 uplink speed as true UMTS. WCDMA and CDMA are based on the principles Qualcomm's CDMA system. The difference will come into the fact that WCDMA does not time sync base and mobile, this will prevent WCDMA system to use the same amount of Welch codes per Mhz. because you will not able to reconstuct the multipath signals as you do in a CDMA system. The higher data rates are up in the air right now, I thought that the specs for UMTS was for 2Meg data, if this is true then the CDMA EV/DO at 1.25Mhz currently does 2Mhz. So the data speeds are not superior with UMTS. Mostly this is a guessing game becasue there are no UMTS mobiles currently selling right now, once the system is loaded and running then we can do a real world comparison with it. CDMA EV/DO and 1XRTT are currently up and running which is more than can be said for UMTS.

    Just my couple of cents.
     
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  6. Carajo

    Carajo New Member

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    Some good points....

    J-Phone does have a UMTS network up right now.. I have seen it...................not really sure how to expand on it [​IMG]

    Yes the prinples of CDMA are applied in both areas but I guess we could discuss the differnces between WCDMA and IS-95 CDMA system all day, you are correct in an a sense for the sync with the mobile and the base station, in IS-95 you sync with the GPS..... the WCDMA system does not use the GPS but WCDMA still needs to sync the mobile with the system and the WCDMA system does combine the multipath signals in both the uplink and downlink (In the mobile and the RNC, a RNC is basically the BSC). I guess we could discuss this all day but not in a very productive way through a forum. I didn't mean that that WCDMA offers high bit rates over CDMA EV/DO and 1XRTT what I ment was that 5MHz compared to 1.25MHz can fit more information into it.... unless you are telling me that 1*1.25Mhz carrier in CDMA can give you the same capacity as a 1*5MHz carrier in UMTS........

    But as for your comments as for CDMA EV/DO and 1XRTT are currently up and running which is more than can be said for UMTS. So what data rates are you getting for CDMA EV/DO and 1XRTT in real live networks in the states. And if they are very high which mobiles support these bit rates?

    The reason I ask is that there is allot of BS about WCDMA, CDMA EV/DO and 1XRTT, GPRS, EDGE etc about the bit rates..... I mean the specs are one thing and real life is another. I felt you where not that impressed with UMTS with 384 Kbps..... are you saying that CDMA EV/DO and 1XRTT support this today? And if so please tell me which mobile that is working with this.
     
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